164 PRACTICAL ORGANIC CHEMISTRY
tap, so as to obtain small crystals of the hydrochloride. The
beaker is placed in a freezing mixture and the contents cooled
below 10°. The sodium nitrite is added in small portions at a
time with stirring, the temperature being kept below 10°. The
hydrochloride gradually dissolves in the form of the soluble
diazonium salt. Towards the end of the operation a drop of the
solution is occasionally tested with potassium iodide and starch
paper when an excess of nitrite is indicated by a blue sta.hi.
The solution is poured very slowly into the solution of caustic
soda previously cooled in ice, so that the temperature does not
rise above 10°.
CH3.C6H4N2C1 + 2NaOH = CH3.C6H4N2ONa + NaCl + H2O.
Meantime the stannous chloride solution is converted into sodium
stannite by adding a 50 per cent, solution of caustic soda until
the precipitate of the hydrate nearly redissolves (about 30grams
of caustic soda). The liquid is placed in a round flask (500 c.c.)
attached to a condenser and cooled^in ice. The alkaline diazo
solution is poured through the top of the condenser in small
quantities at a time. After each addition there is a vigorous
effervescence and evolution of nitrogen,and a brown oil separates
which consists of impure toluene.
CH3CGH4NoONa + Sn(ONa)2 + H2O = CH3.C6H5 + No + NaoSnO.,
When the solution has all been added the toluene is distilled off
in steam, separated from the water, and dehydrated over calcium
chloride. It distils at 110°. Yield 5—6 grams.
Griess, Annalen, 1866, 137, 39; Ihle, /. prakt. Chem.^ 1876,
25 grms. /-toluidine.
2-5 „ cone, sulphuric acid (in 750 c.c. water).
20 „ sodium nitrite (in 40 c.c. water).
Mix the dilute sulphuric acid and toluidine in a large round
flask (ij litre) and cool to the ordinary temperature. The nitrite